Sustainable Facilities Tool General Services Administration

Alternate Water Harvesting Systems

Alternate water harvesting systems – Alternate water harvesting systems capture water from on-site sources other than fresh surface and groundwater.  Alternate water is typically minimally treated and used in non-potable applications such as landscape irrigation, cooling tower makeup, and plumbing fixture flushing. As a result, successfully implementing an on-site alternate water harvesting system can significantly reduce potable water consumption. Examples of alternate water include:

• Rainwater – Water stemming from rainstorms but not subjected to ground contaminants. The source is typically collected from the roof and can be subjected to minor purification by percolating through the layers of a green roof.
• Greywater – Wastewater from showers, faucets, and clothes washing machines that typically does not include solid particulates. Blackwater, or sewage from toilet and urinal processes, is not an acceptable alternate water source without significant on-site treatment. Grey water is regulated on state-by-state basis. Work with local water jurisdiction officials to get approval for grey water projects.
• Condensate – Water droplets accumulated through condensation on cooling coils in air handling units (HVAC equipment) can be collected and reused; often cooling tower makeup is a good application for this alternate water source because of its high quality and often close proximity to the building’s cooling tower.
• Stormwater – Water collected from the building’s stormwater drainage system can be collected and treated; the level of treatment required depends on the amount of pollutants and debris that the stormwater is exposed to and the intended application. .
• Sump water – Water collected at the foundation of the building and pumped away to avoid flooding can be collected and reused; since sump water typically has less contamination, less treatment is often required.

Bundles: Optimize Water Systems Landscaping: Conserving Water & Reducing Waste Landscaping: Conserving Water and Reducing Waste

System Relationships

Landscaping/Irrigation

The landscape surrounding the building envelope can have significant water use depending on the building’s location and landscape design. Designing a landscape that requires minimal supplemental water (through considerate planning and selection of climate-appropriate plants) reduces the demand for on-site irrigation. Xeriscaping should be considered, which is a set of principles including efficient minded design, native and adaptive planting, proper soil amendments, and pro-active landscape maintenance. Xeriscaping can practically eliminate irrigation needs, which should be the goal of any water project. For the areas needing supplemental water, use a water-efficient irrigation system with advanced controls that determine the proper amount of water needed by the landscape based on real-time weather conditions and soil moisture. Exterior water features such as fountains should utilize alternate non-potable water sources.

Find products used to contain, maintain or enhance landscaping products in the Green Procurement Compilation.

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System Relationships

Piping

Water is distributed throughout the building by a network of pipes. Pipes can move water for domestic, HVAC, and fire protection needs. Well-designed and maintained piping systems help reduce pump size, save energy, and minimize water lost through the system by optimizing the network through:

• proper sizing
• minimizing the number of joints and turns
• detecting and repairing water and steam leaks
• providing proper insulation on steam and hot water lines to avoid undesirable heat transfer. 

Bundles: Optimize Energy Efficiency

System Relationships

Boilers/Steam System

Boiler and steam generators are commonly used in large heating systems or facilities where large amounts of process steam are used. Steam is often used for heating or in large kitchens. Steam condensate return and automatic blow-down systems reduce water use, energy costs, and chemical use. Steam and hot water may be circulated throughout the building or grounds. These systems are subject to leaks that can contribute to water consumption. Utilizing chemical free treatments for boilers and condensers allows water to be used elsewhere without additional treatments.

Bundles: Optimize Energy Efficiency Planted Roofs & Hot Water

Humidification

Your HVAC system may have equipment to add moisture to the air during dry conditions, leading to greater occupant comfort and reduced static in the building (which can affect computers and other electrical devices). Certain dry climates can make use of the cooling provided by evaporation, and HVAC systems can be designed to provide much of the building’s cooling needs with humidification alone. Avoid airborne water losses by ensuring that the building envelope is appropriately sealed so that humidified air is not lost to the outside.

System Relationships

Cooling Tower

Drinking Water

Water coolers and water fountains deliver drinking water to building occupants. Each water fountain typically has its own compressor and refrigerant system to cool water. However, running these fountains all day with many small systems may be less efficient than a central water chiller and filtration system. Water that is delivered, in large water cooler bottles or single-serving bottles increases waste and transportation-related fuel use.

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System Relationships

Kitchen Processes

Kitchen processes such as pre-rinse spray valves, dishwashing, ice making, steam-based heating trays, and garbage disposals all have environmental implications pertaining to the water system.

• Pre-rinse spray valves: Install high efficiency pre-rinse spray valves that do not exceed 1.25 gpm.
• Dishwashers: Run the dishwasher only when at full capacity and specify ENERGY STAR appliances, which not only reduces overall water consumption but also the associated energy needed to operate and heat the water.
• Ice machines: Install only ENERGY STAR qualified ice machines; consider retrofitting once-through water-cooled ice making machines to a closed loop system.
• Food steamers: Ensure tight fits between food trays and heating trays to reduce steam loss; when installing new equipment, install ENERGY STAR qualified connectionless food steamers that are significantly more water and energy efficient than boiler-based equipment. 
• Garbage disposals: Retrofit disposals with solenoid valves and automatic controls that only run water while the disposal is operating; reduce the water used to convey food waste via conventional garbage disposals with strainers or mesh screens to collect food waste and use it for compost. 

Be familiar with the requirements for FEMP designated kitchen equipment. Use the SFTool Green Procurement Compliation to find kitchen process products, including cafeteria services and non-paper office products.

System Relationships

Sewage Discharge

Once the water within the building reaches its end use, it is discharged to a sewage treatment facility to be eventually discharged to water bodies. Sewer fees are frequently more expensive than water consumption bills. Water-efficient equipment and water reuse strategies may limit the quantity of water sent to the treatment plant. On-site treatment may allow for additional on-site uses of waste water, such as irrigation or toilet flushing, which can be environmentally and fiscally preferable as sewage utility rates continue to rise.

Domestic Hot Water

Potable water is heated for use in showers and sinks. Water-efficient fixtures help reduce the amount of energy needed to heat this water. Leaks in the domestic hot water system are particularly expensive, as both water and energy are lost in the process. Typical domestic water heating strategies include:

• Central – A central boiler and pump system distributes hot water throughout the building. These systems are good for buildings with large and relatively constant hot water needs.
• Tank – This type of water heater is common in the home, with a gas or electric heat source and capacity for water storage. Energy is needed to keep this water hot, even if it is rarely used.
• Instantaneous/Tankless – These typically small heaters are placed close to the delivery point of hot water, such as under a sink. Tankless units do not store hot water; rather, they heat water as it passes through the unit on the way to its nearby destination. These units require a short but high power demand to heat the water quickly and are a good choice where hot water needs are infrequent.

Consider whether solar hot water heating is appropriate. The Energy Independence and Security Act of 2007 requires that no less than 30 percent of the hot water demand for each new Federal building or major renovation must be met through solar hot water, if lifecycle cost-effective.

System Relationships

Plumbing Fixtures

Plumbing fixtures - Plumbing fixtures such as toilets, urinals, faucets, and showers dispense water to building occupants for hygienic, cooking, or similar purposes. Implementing a fixture replacement and retrofit policy with technologically-advanced water-efficient fixtures significantly reduces overall water consumption. Alternatives to conventional fixtures include WaterSense labeled or label-eligible product types such as:

• Toilets – high efficiency toilets that use no more than 1.28 gallon per flush (gpf) including WaterSense labeled tank, pressure assisted, and dual-flush toilets, high efficiency flush valve toilets, and composting toilets
• Urinals – high efficiency urinals that use no more than 0.5 gpf including flush valve and non-water urinals
• Faucets – private WaterSense faucets that use no more than 1.5 gallon per minute(gpm); public faucets that use no more than 0.5 gpm
• Showers – high efficiency WaterSense showerheads that use no more than 1.5 gpm

Reducing the amount of heated water for faucet and shower applications also leads to energy savings.

Bundles: Optimize Energy Efficiency Optimize Water Systems Human Behavior

System Relationships

Pumps

Pumps are devices that use a motor to move a fluid from one place to another. In the context of buildings, pumps typically refer to the movement of water through pipes. Water often needs to be moved vertically or across long horizontal distances for use, such as the cold water originating from the chiller that needs to get to the air handling unit in order to cool rooms in the building. Pipe size, material, and routing through the building all affect the workload for a pump. Pumps should be sized to operate at peak efficiency under conditions it will experience most often. Pumping systems can be made more efficient by using variable speed drives to use less energy during partial loads. See more tips for pump efficiency in the Federal Energy Management Programs “Operations & Maintenance Best Practices” guide.

Boiler

Boilers use electricity, natural gas, or other energy sources to heat water or create steam for heating systems throughout the building. Dissolved solids precipitate out as water evaporates within the boiler, causing scale to build up in the system that reduces system efficiency.  Water is rejected from the boiler, known as “blow down”, to reduce scale build up and fresh water is added, known as “make up”.  The ratio of impurities¹ in the blow down to make up water is known as “cycles of concentration”.  The higher the cycles of concentration, the less make up water is required.  Consider the following measures to increase the cycles of concentration and water efficiency of boilers:

• Institute water treatment program to reduce the buildup of dissolved solids and increase cycles of concentration
• Ensure that there is a well-maintained condensate return loop on steam systems that sends captured condensate via steam traps back to the boiler, which will in turn reduce energy and water use
• Install an automatic blow down and chemical feed system that rejects water based on specific water quality thresholds

If you are in need of a new boiler, choose a high efficiency option. The average existing boiler loses 24% of the energy intended for heating right out the flue, before it does any useful water heating. Modern boilers can exceed efficiencies of 90%.² Maintenance is key to proper boiler operation. See tips on how to keep your boiler system running well in the Operations and Maintenance section.

²US EPA - ENERGY STAR Building Upgrade Manual

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